Soaking the onion takes away its bite and pulls its sweetness to the forefront.
Source: Everyday Food, 2011
1 small red onion, very thinly sliced
5 ounces rustic bread, torn into 3/4-inch pieces (about 4 cups)
2 pints (10 ounces each) grape or cherry tomatoes, halved
1 small garlic clove
1/2 cup extra-virgin olive oil
2 tablespoons red-wine vinegar
1/2 English cucumber, halved lengthwise and thinly sliced
2 celery stalks, thinly sliced crosswise
4 radishes, thinly sliced
1 cup fresh basil leaves (from 1 bunch)
1/2 cup fresh parsley leaves
2 tablespoons salt-packed capers, rinsed, soaked in cold water, rinsed again, and minced
Preheat oven to 450 degrees. In a small bowl, cover onion with cold water. Swish water around, rubbing onion slices with your hand. Drain and repeat 2 or 3 times, letting slices soak and changing water every 10 minutes. Drain onion; pat dry. Arrange bread in a single layer on a rimmed baking sheet. Bake until edges are crisp and golden, 6 minutes. Let cool completely on sheet on a wire rack; transfer to a large bowl. Add tomatoes and 1/2 teaspoon salt; let sit 10 minutes.
Meanwhile, finely chop garlic with a generous pinch of salt. Drag the blade of a large knife at an angle across mixture until a paste forms. Transfer to a small bowl and whisk in oil and vinegar. To tomato mixture, add onion, cucumber, celery, radishes, basil, parsley, capers, and dressing; toss to combine. To serve, season with salt and pepper and toss.